#include <cstdio>
#include "iostream"
using namespace std;

int main()
{
    double n;
    cin>>n;
    double l=-50,r=50,mid,eps=1e-8;
    while(r-l>eps){
        mid=(r+l)/2;
        if(mid*mid*mid>n)
            r=mid;
        else l=mid;
    }
    printf("%.6lf",mid);

}
